The succinimides are detergent-dispersant additives for lubricating oils. They are prepared by reacting maleic anhydride with a polybutene with a molecular weight in the range about 700-1000. The polybutene double bond adds to the double bond of maleic anhydride in what is generally known as a "pseudo Diehls-Alder addition." This saturates the double bond of the maleic anhydride but leaves a double bond in the polybutene chain, close to the point of addition. This reaction produces a polybutene succinic anhydride. The succinimide is prepared by reaction of the polybutene succinic anhydride with an ethylene amine such as ethylene diamine, diethylene tramine, triethylene tetramine, etc., or with ethylene amine mixtures. There is a rather wide compositional spectrum of succinimides, polybutene molecular weight may be varied, the ethylene amine reactant may be varied, the mol ratio of polybutene succinic anhydride to ethylene amine may be varied and variations in tne mol ratio and reaction temperature produce imide-amide mixtures. While there are variations in precise compositions of succinimide additives, the processes by which they are produced have in common a final step of filtration of the succinimide reaction product using a filter aid, a siliceous material, usually diatomaceous earth.
The succinimide reaction product is a solution of the succinimide in oil (usually a lubricating oil) used as a reaction medium or added to the reaction product prior to filtration and suspended in the solution, particles of insoluble materials produced in the reaction. Filtration of the reaction product removes the insoluble material and results in the production of a filter cake having a substantial content of oil and succinimide. These filter cakes have been regarded as a waste material presenting a disposal problem. The present invention provides a process for treating these filter cakes to recover the contained oil and succinimide.